Overexpressed mitochondrial hinge protein, a cytochrome c-binding protein, accelerates apoptosis by enhancing the release of cytochrome c from mitochondria.
Holocytochrome c released from mitochondria has been revealed to be one of the contributors of apoptosis. To investigate how the cytochrome c protein is released from mitochondria, we examined the effects of overexpression of the hinge protein, a cytochrome c-binding protein, or cytochrome c on apoptosis by introducing their cDNAs under a constitutive promoter. Overexpression of the cytochrome c and hinge protein mRNAs was confirmed by Northern blotting, although marked accumulation of the cytochrome c protein was not observed. In transfectants of the hinge protein gene as well as cytochrome c gene, apoptosis was accelerated as judged by FITC-conjugated Annexin V binding to the cell surface and DNA fragmentation. In addition, enhancement of the release of cytochrome c into cytosol was demonstrated in these transfectants by a subcellular fractionation experiment, followed by Western blotting. These findings suggest that the release of the cytochrome c protein from mitochondria is regulated by the hinge protein involved in the respiratory chain in the apoptotic process.
Okazaki
M
M
Department of Biochemistry and Cell Biology, Nippon Medical School, Kanagawa, Japan.
Ishibashi
Y
Y
Asoh
S
S
Ohta
S
S
D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D003574:Cytochrome c Group / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation; D004579:Electron Transport; D014450:Electron Transport Complex III; D015870:Gene Expression; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000502:physiology*; D011485:Protein Binding; D011506:Proteins / Q000235:genetics* / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D014162:Transfection
D017304:Annexin A5; D003574:Cytochrome c Group; D011506:Proteins; D012333:RNA, Messenger; C039762:UQCRH protein, human; D014450:Electron Transport Complex III